This invention relates to video imaging, and, more particularly, to video cameras used for generating video images.
The advent of the video age was engendered by the development of the video camera. This device, which was originally in the form of a special video vacuum tube, produces output voltage variations that are proportional to a video image focused on it. In the case of modern video cameras, the output voltages include signals proportional to the intensity of the signal as well as to the color content of the signal. Modern technology provides these signals from solid state devices, such as a charge coupled device (CCD), wherein a stored-charge image is developed on a silicon chip which is scanned out by a solid-state array overlaid thereon.
A variety of formats are available for characterizing these signals, such as "YIQ" which is the United States' video broadcast standard format as developed by the National Television Systems Committee (NTSC). Another choice, developed in Europe, is the "YUV" format which is most often used in digital video systems worldwide.
When a video signal is first generated, it is an analog signal with multiple components necessary for reception thereof. In particular, a typical video camera provides at its output a "composite" analog video signal containing six components: (1) horizontal sync, (2) vertical sync, (3) composite sync, (4) luminance, and (5) and (6) the two chrominance signals. The sync signals are necessary in order for an analog receiver to "lock in" on the video signals so that the sequential frames of video data can be displayed logically on the receiver's video screen. A typical analog video signal, in the standard "RS-170" format, is depicted in FIG. 1.
There are two main aspects of the traditional analog video signal that make it somewhat difficult to deal with: first, since the signal is analog, each time it is reproduced or "repeated" its distortion levels increase and its signal-to-noise ratio decreases; and, second, the receiver must be specially set up to synchronize with the particular analog sync signals.
The difficulties encountered in dealing with analog video signals are disclosed, for example, in U.S. Pat. No. 4,905,085 issued to mark E. Faulhaber on Feb. 27, 1990, entitled "Synchronous Sampling System." The complexity of the so-called "frame grabber" circuitry described therein exemplifies the need for and convenience of having an alternative serial digital signal that represents the video image in a computer-friendly format.
It is therefore an object of the instant invention to provide a video camera that produces a digitally-coded output signal in the form of a serial digital message that can be conveniently repeated without adding distortion or noise, and that does not require special synchronization apparatus for reception, and that can be conveniently digitally buffered or stored as desired.